The present invention relates to touch sensors and, more particularly, to a method for detecting erroneous key selection when, for instance, a user's finger touches two adjacent keys of a key pad.
Touch sensor user interfaces, typically in the form of a designated touch sensitive keypad or touch screen, have been incorporated into a variety of electronic devices such as cellular telephones, portable entertainment devices and computers. Typically, a touch sensor user interface has a plurality of touch actuated sensors associated with a user input region typically comprising input keys. For example, a cellular telephone (touch screen smart phone) may include a touch sensor user interface with an array of input keys, with twenty six of the keys being designated to letters of the alphabet, ten of the keys being designated to each of the numbers from 0 to 9, and further addition keys being designated to punctuations, special symbols and function instructions.
Touch sensor user interfaces such as touch screens have a display area operable to detect the presence and location of a touch within the display area. The term touch generally refers to a contact to the display area by a finger or object such as a stylus or pen. Such touch screens typically work on the effects of a matrix of capacitors or resistors in which the capacitance or resistance variations within the matrix vary at the point of contact. From these variations, row and column coordinates of the matrix are determined and thus a key displayed on the screen at those coordinates can be determined. However, using this approach the identification of an actuated key can be relatively computationally complex especially for high resolution touch screens as many matrix coordinates can be associated with a single key.
One approach that reduces the computational complexity of determining an actuated key of a touch screen or designated touch sensitive keypad is by a firmware coded configuration. With such a configuration, each key is partitioned into two coded sub-regions and each sub-region has one or more detectors directly connected to an input of a processor. When both sub-regions detect concurrent contact from an object, the processor identifies the actuated key from signals sent from two sub regions. This approach is relatively computationally efficient. However, the coding of the sub-regions can result in erroneous keys being identified by the processer when, for instance, a finger touches one sub-region of a first key and another sub-region of an adjacent second key.